1. Field of the Invention
The present invention relates to a scroll type booster connected to a pneumatic line in a plant, which is preferably employed as a booster for intensifying the pressure of a fluid such as air where appropriate.
2. Description of the Related Art
Generally in a plant where a plurality of pneumatic apparatuses are installed, the apparatuses are connected with one another using a pneumatic line (piping) such that compressed air discharged from an air compressor serving as a compressed air source is supplied to the respective pneumatic apparatuses via the pneumatic line. The air pressure within the line at the downstream side is boosted using a reciprocating compressor, a so-called booster type compressor, as disclosed in Japanese Unexamined Patent Application Publication No. 2007-51614.
The aforementioned reciprocating compressor allows a piston to move reciprocally inside a cylinder to discharge intake air compressed therein. The compressor is likely to be a source of noise as the operation sound resulting from the discharge of air is loud, thus deteriorating the peripheral work environment.
In contrast, a scroll type fluid machine, known as a noiseless compressor, has a lower operation sound volume than the reciprocating compressor. With a scroll type compressor, an orbiting scroll is driven by a drive unit such as an electric motor to turn with respect to a fixed scroll such that the fluid such as air may be continuously compressed within a compressor chamber arranged between the scrolls as disclosed in Kokai-Giho (Journal of technical disclosure) No. 2006-504219.
The scroll type compressor as described above includes a magnet between the opposing surfaces of the fixed scroll and the orbiting scroll. The magnetic force of the magnet is used to restrain the displacement of the orbiting scroll before starting the compression operation, for example, minimize rattle or vibration of the orbiting scroll by an amount equal to the axial gap (play).
As the aforementioned magnet, the use of an electromagnet such as a solenoid has been proposed. When such an electromagnet is employed, the power supply to the electromagnet is stopped when required, for example, at the start-up of the compression operation to stop generation of the magnetic force to allow the orbiting scroll to be more smoothly moved (orbiting movement).
In the structure disclosed in Kokai-Giho (Journal of technical disclosure) No. 2006-504219, the magnetic force of the magnet serves to restrain rattle or vibration of the orbiting scroll in the axial direction under the action of the external force before starting the compression operation.
In order to obtain sufficient restraining force from the magnetic force of the magnet, the magnet is required to be large enough to support the weight of the orbiting scroll. The resultant magnet, thus, becomes expensive. The use of a structure of this type is not necessarily an effective solution in terms of cost-effectiveness.
When the magnetic force of the magnet acts upon the orbiting scroll during the compression operation (steady operation), the resistance against the driving operation of the orbiting scroll to orbit is generated to adversely influence the magnetic force. This may increase the start-up load, the mechanical loss, and finally, deteriorate the operation efficiency.
Meanwhile, when an electromagnet such as a solenoid is employed, power supply is stopped upon starting of the compression operation to stop generation of the magnetic force to compensate for the smooth movement of the orbiting scroll. In this case, however, an electromagnet which is large and expensive is required. The use of its structure, thus, is not necessarily a realistic solution in terms of cost-effectiveness.
In the aforementioned case, the electric wiring for power supply to the electromagnet is required to be installed at the fixed scroll, which makes the structure of the scroll type compressor complicated. It is therefore difficult to realize a compact and lightweight structure.